1. Field of the Invention
The present invention relates to a novel azo compound, its metal complex compound, a water-soluble azo dye containing the same, and a polarizing film having a high polarization degree in which the above-mentioned dye is contained and oriented as a dichromatic dye in a polymer film.
2. Description of the Prior Art
As a polarizing element for use in a polarizing film, iodine has heretofore been used, and in recent years, the utilization of organic dyes has also been investigated.
However, iodine which has heretofore been used has a high polarization performance, but since having large sublimation properties, iodine is disadvantageously poor in heat resistance, when added as the polarizing element to a polarizing film.
In order to overcome this drawback, there have been suggested some polarizing films containing organic dyes as the polarizing elements and having improved heat resistance in Japanese Patent Publication Nos. 61988/1990 [CA 102(4): 26357w], 50944/1992 [CA 104(10): 70283j], 61893/1992 [CA 104(10): 69953w), U.S. Pat. No. 4,514,559, Japanese Patent Application Laid-open Nos. 269136/1990 (U.S. Pat. No. 5,007,942), 222459/1990 (U.S. Pat. No. 5,272,259), 226162/1992 (U.S. Pat. No. 5,122,557); 68902/1991 (CA 115(24): 266442g) and 89203/1991 [CA 116(22): 224369d).
However, such polarizing films are not always satisfactory from the standpoint of polarizing performance.
Thus, it is desired to develop a dye for a dye-based polarizing film which can exert the polarizing performance comparable to that of an iodine-based polarizing film.